The present invention relates, in general, to a method of treating intervertebral discs to relieve back pain and, more particularly, a method of treating an intervertebral disc by heating the damaged portion of an annulus of the intervertebral disc with light energy while optically monitoring temperature as the damaged portion of the annulus is heated.
Degenerative disc disorders are difficult to treat. The normal pathway for treatment of lower back pain starts with a number of minimally invasive treatments including medications and exercise. Spinal surgery, such as spinal fusion or ablation of the nucleus, can also be used, but such surgeries are generally avoided because they are very invasive. A less invasive procedure is percutaneously applying heat to the annulus of an intervertebral disc.
Damage to the intervertebral disc in the spine is the main cause of lower back pain. The intervertebral disc, sometimes called a spinal disc or a disc, is a capsule with an annulus, comprising collagen, surrounding an inner volume called the nucleus. The nucleus contains a gel-like material. Damage to the annulus triggers the body to attempt to repair the injury. The repair attempt results in blood vessels and nerves growing into the damaged area of the annulus. It is believed that these new nerve endings are the source of xe2x80x9cdiscogenic painxe2x80x9d and low back pain. Damage to the annulus also can result in weakening and bulging of the intervertebral disc. If the bulging puts pressure on nerve roots from the spinal cord, the result is pain and nerve dysfunction.
It is well known that collagen responds to heat by shrinking and stiffening. In a damaged intervertebral disc where the damage has resulted in a bulge, heating the annulus to shrink the collagen in the annulus can help reduce the bulge. Heating the annulus to stiffen the collagen is also beneficial because the stiffer annulus reduces excessive movement of the spine. In addition, the heat applied to the annulus to shrink the collagen is beneficial because it damages or destroys nerve endings that may have grown into the damaged annulus, thereby reducing the ability of the nerves to transmit pain. The combination of shrinking the collagen in the annulus and damaging or destroying the unwanted nerve endings is thought to be beneficial in reducing back pain.
Physicians have treated intervertebral disc pain utilizing radiofrequency current and lasers to heat the nucleus of a disc to a temperature high enough to damage nerve endings that have grown into the annulus. The heated nucleus transfers heat to the annulus of the intervertebral disc to raise the temperature of the annulus to a level that damages the unwanted ingrown nerve endings. U.S. Pat. No. 5,433,739 to Sluijter et al describes a method of treating disc pain by utilizing radiofrequency current to heat the nucleus of an intervertebral disc. Sluijter et al, in the ""739 patent, describes the use of electronic temperature measurement devices to monitor temperature of the intervertebral disc. In U.S. Pat. No. 5,571,147, Sluijter et al describe a method of heating the nucleus of the intervertebral disc using laser light with electronic temperature monitoring.
Physicians have also treated disc pain by ablating the nucleus to reduce pressure placed on the annulus by the nucleus. Physicians have utilized lasers to ablate or vaporize the nucleus of an intervertebral disc. U.S. Pat. No. 5,958,008 to Daikuzono describes using a laser to vaporize the nucleus of an intervertebral disc. Daikuzono monitors temperature electronically.
Physicians have also treated disc pain by utilizing an electrically heated wire placed into an intervertebral disc to heat the annulus of the intervertebral disc to a temperature sufficient to cause the collagen in the annulus to shrink. The wire, which is heated through resistive heating, transfers heat by conduction to surrounding tissues. U.S. Pat. No. 6,122,549 to Sharkey et al describes a method to treat disc pain utilizing thermal resistive electric heating. The ""549 patent of Sharkey et al discusses the use of electrical temperature measurement elements in the resistive heated wire to assess tissue temperature.
Faster heat transfer and lower heating times are achieved by radiating light energy to heat a portion of the annulus instead of conducting heat energy from a heated wire. The quicker radiation heat transfer by light energy has the benefit of raising the temperature of targeted tissues to a therapeutic level more quickly, reducing the likelihood of damage to non-targeted tissues such as the spinal cord or nucleus.
When using diffuse light energy to heat, optical temperature measurement would facilitate a more accurate reading of the temperature than does electrical measurement. Optical temperature measurement devices absorb very little energy from illuminating light rays and so do not self heat, a problem encountered with metallic temperature measurement devices such as, for example, thermocouples. The temperature measured optically is substantially the temperature of the tissue near the temperature measurement device and not a temperature induced by optical illumination directly on the device. Optical temperature control and feedback closely controls the zone of heating so that a surgeon can use diffuse light energy to selectively heat a damaged portion of an annulus.
A method of using diffuse light energy combined with optical temperature measurement carries the advantage of utilizing only light-carrying components within the patient, thus eliminating the concerns many physicians have with inserting electrically conductive components and electrical energy into the spine. It also eliminates problems faced when some electrical ablation systems are used, such as grounding.
It would, therefore, be advantageous to develop a method of controllably heating a region of an annulus of an intervertebral disc using diffuse light energy and optical temperature measurement. It would further be advantageous to develop a method of heating the collagen in the annulus of an intervertebral disc utilizing diffuse light energy and optical temperature measurement with feedback control.
The present invention is directed to a method of heating the annulus of an intervertebral disc by using a light source to emit diffuse light energy and optically measuring the temperature of the heated tissue. The present invention is further directed to a method of controllably shrinking collagen in the annulus of a intervertebral disc by using a light source to emit diffuse light energy, optically measuring the temperature of the heated tissue, and adjusting light intensity based on the measured temperature. In particular, in a method according to the present invention, an optical fiber including a diffuser is placed into the intervertebral disc percutaneously through a small diameter hollow needle or trocar. The fiber is maneuvered within the intervertebral disc""s nucleus to an area near a damaged portion of the intervertebral disc""s annulus. A light generator, such as a laser, is programmed to deliver light energy to raise the temperature of a region of the annulus tissue to a predetermined temperature for a predetermined length of time. The temperature can be, for example, temperature sufficient to produce shrinkage of collagen in the annulus of an intervertebral disc or a temperature sufficient to produce nerve damage of ingrown unwanted nerve endings in the annulus of an intervertebral disc. In an optical fiber and light generator useful for an embodiment of the present invention, temperature monitoring of tissue near the optical fiber can be accomplished using fluorescent material placed at the end of the optical fiber. The fluorescent material, when illuminated with a light having a predetermined wavelength, fluoresces with a light that decays in intensity with a time-delay dependent upon the temperature of the fluorescent material, which is substantially equal to the temperature of the tissue near the fluorescent material. Computerized control within the light generator monitors the returned fluorescent signal and controls power output and light intensity to control temperature of tissue near the diffuser. A method according to the present invention further includes heating the annulus using an advantageous optical fiber that includes a continuous, unitary outer sleeve.
Detailed illustrative embodiments of laser fibers for implementing the present invention are disclosed. However, it should be recognized that various alternate structural elements may occur to those skilled in the art, some of which may be different from those specific structural and functional details that are disclosed.